Technical Abstract:
A decade ago sudden death syndrome (SDS) of soybean received only minor attention by growers and researchers in Illinois and in other states. In the last decade, SDS has become a major disease and research programs have been developed to understand the pathogen, disease development, and how to control the disease. SDS is readily recognized by its distinct symptoms that include mottling and interveinal chlorosis and necrosis on the upper leaves at flowering. It also causes root and crown rot, vascular discoloration of stems, defoliation and pod abortion. A soilborne fungus, Fusarium solani f. sp. glycines, causes SDS. Field patterns of SDS vary from strips, distinct patches, to large extensive patches that coalesce to cover extensive areas in any one field. The foliar symptoms of the disease are normally observed on plants during the mid to late reproductive growth stages from mid to late August. State surveys in 1998 and 1999 showed that SDS occurred in all agricultural statistics districts in Illinois with some districts having as high as 46 and 68% of fields with SDS in 1998 and 1999, respectively. Because of the high incidence and increase of inoculum, the disease is likely to remain a major constraint to increased yields. Our research has focused on reducing the occurrence of this disease through soybean varietal selection, breeding and other means of cultural controls. Every year commercial varieties and other germplasm are screened and scored for resistance to SDS. Varietal selection is at this time the best option in managing this disease.